I have a 2001 Ford E-350 shuttle bus that's about 21 ft long (bumper to bumper) and I'm piecing together parts for an A/C system for the rear (the front has the stock A/C system). This bus used to have a rear AC system made by Carrier but a lot of it was rotten and corroded (especially the condenser unit) from operating in the mid-Atlantic region (winter salt), so I ripped it all out when I moved to an area where the temps rarely got above 80 F. However, now I've moved again and driving through states like Nevada, Arizona and Utah is a pain during the summer so the bus needs rear A/C again.
So I'm posting this as a sanity check on parts, thermal ratings, etc.. and to see if you guys have any inputs and suggestions. And for what it's worth, the rear passenger volume is not well insulated (lots of windows) and measures about 16 ft long, 6 ft wide, and about 7 ft in height (560 cu-ft).
To start, the compressor for the rear is going to be a TM-21 compressor which has a displacement of 13 cu-in.
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According to a Trans-Air PDF guide, a 13 cu-in compressor should be able to handle 60k BTU.
https://www.transairmfg.com/pdfs/BK-BTU-0626141.pdf
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WIth that 60k compressor capacity in mind, for the condenser, I'm leaning towards the Trans-Air SMC2S which has a capacity of 59k BTU, although the SMC3L is an option (if I can fit it in the "skirt" area) and has a capacity of 87k BTU.
- condenser_capacity.png (162.94 KiB) Viewed 959 times
So this leads to my first question: with the compressor capacity and rating in mind (60k BTU), does it make sense to even pursuit trying to fit the larger capacity SMC3L (87k BTU) or should I just go with the smaller SMC2S (59k BTU) ? Price wise, the two units aren't too far apart so would the larger condenser unit allow the system to operate with less duty cycle on the condenser fans (and alternator load) ?
As for the evaporator unit itself, I'm planning on building the unit assembly (have a vertical mill, a lathe, TIG welder, etc..) from off the shelf evaporators that are readily available from auto parts stores. My thought is to use two of 4-Seasons 44163 (as an example) and tie them together so that the output of one evaporator goes into the input of the second evaporator (parallel or inline ? ) right next to each other and have a long blower fan operating across both evaporators. Due to space limitations, I'm trying to keep the entire evaporator assembly no greater than 8 inches in height (length and width isnt as big of a constraint) so the 4-Seasons 44163 fits that bill. Thoughts on this idea of using two evaporators right next to each other (either in series or parallel, or back to back to form a thicker "core" ) ? There are off the shelf evaporators that are longer and meets the height constraint but they are significantly more expensive (like the Red Dot ones) and might be difficult to replace in the future.
4-Seasons 44163 : Rule 8
Now for the TXV, what tonnage would you guys recommend? I'm comparing this to systems from Trans-Air and Red-Dot and it looks like most of them are in the 2-4 ton range. Does that make sense, or is this a 5 ton system (60k / 12k = 5) ?
Thanks for taking the time to read my post and I'm glad to take any inputs and suggestions you guys may have.
